Method of manufacturing a coil

ABSTRACT

A coil having several turns of an insulated conductor is provided with a shrinkage tube of insulating material by producing such relative movement between the conductor and the tube that the end of the conductor passes into the tube and through it a number of times until a portion of all the coil turns is enclosed within the tube. The tube, which may be corrugated to shorten its length during the winding operation, is then heated beginning at one end and expands along and contracts over the wound coil.

United States Patent Virsbreg A I [54] METHOD OF MANUFACTURING A COIL[72] Inventor: Lars-Goran Virsbreg,

Sweden 731 Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras,Sweden 22 Filed: Feb.16, 1971 21 Appl.No.: 115,290

Vasteras,

301 Foreign Application Priority Data Sweden ..2335/70 Feb. 24,1970

s2 U.S.Cl ..29/605,29/596, 174/1310. 8, 242/103, 336/209 511 im. on...H0lf7l06 [58] Field of Search ..29/605, 596; 242/4 A, 4 B, 242/703,7.07; 336/209; 174/DIG. 8

[56] References Cited UNITED STATES PATENTS 3,164,888 l/ 1965 Sharrowetal .29/605 X [451 Nov. 14, 1972 3 ,436,8 1 5 4/1969 I Sheets ..,..29/605 3,559,899 2/1971 Fahrbach ..242/4 3,470,046 9/1969 Verdin .Q l74/DlG. 8

Primary Exarniner-Charles W. Lanham Assistant Examiner -carl E. HallAttomey-Jennings Bailey, Jr.

[ ABSTRACT A coil having several turns of an insulated conductor isprovided with a shrinkage tube of insulating material by producing suchrelative movement between the conductor and the tube that the end of theconductor passes into the tube and through it a number of times until aportion of all the coil turns is enclosed within the tube. The tube,which may be corrugated to shorten its length during the windingoperation, is then heated beginning at one end and expands along andcontracts over the wound coil.

11 Claims, 6DrawingFigures PATENTEDWM I912 3.702.499

sum 1 or 2 INVENTOR.

LABS-Goa AN VlRgBZRQ METHOD OF MANUFACTURING A can. BACKGROUND OF THEINVENTION 1 Field of the Invention The present invention relates to amethod of manufacturing a coil comprising several Several turns of aninsulated conductor and provided with at least one layer of insulatingmaterial surrounding all the turns, for examplehigh voltage insulationhaving a dielectric strength of 2,000 volts.

2.-The Prior Art It is known that, instead of insulating a conductorwith tape wound on, it is possible to provide the conductor withaso-called shrinkage tube so that an absolutely tight and uniformconductor insulation of high quality can be produced. The expressionshrinkage tube" usually refers to a tube made of insulating material andhaving the characteristic that a brief heating of the tube causes strongradial contraction of it, for example corresponding to a decrease in theinner diameter of 50 percent. Shrinkage tubes can be-obtained in highquality insulating material, for example silicon rubber.

When manufacturing closed coils for high voltage it is usual to use aninsulating layer surrounding the coil, as well as conductor insulationproviding insulation between the different turns of the coil.

In arranging an insulating layer around a closed coil, it is usual towind insulating tape around the coil crosssection with a certain amountof overlap. Even if shrinkage tape (which shrinks upon being heated) of,for example, silicon rubber, is used, it is difficult to prevent airfrom being enclosed between the various layers or turns of theinsulating tape and with this method a high quality high voltageinsulation requires great accuracy of winding if uniformity and absolutetightness are to be achieved. These disadvantages also apply withinsulations of foil material which is placed against the coil surfaceand attached by winding on a tape, for example as shown in the GermanPat. No. 1,221,358.

,It is also known to embed a closed coil in epoxy resin or the like.However, this method gives relatively high manufacturing costs,particularly when the manufac turing program covers a considerablenumberof coils differing in shape and/or size.

SUMMARY OF THE INVENTION With a method according to the invention therelationship between manufacturing costs and quality is in many casesconsiderably more favorable than in cor responding known methods.

The invention is characterized in that one such layer consists of ashrinkage tube of insulating material, for example silicon rubber, andthat the tube is fitted in expanded state over one end of the conductorand that a continuous relative movement is effected between conductorand tube along a length of conductor corresponding to the sum of thelengths of the various coil turns and that each time such a length hasbeen passed the tube is fitted over said end of the conductor, and thatthe tube is finally shrunk to exert pressure on the bundle of conductorsinside.

According to a further development of the invention aspecial machineprocess is used when winding the coil. According to another developmenta corrugated,

almost bellows-shaped shrinkage tube is used so that the heat-treatmentused for shrinking the tube also causes a considerable increase in thelength of the shrinkage tube. This is an advantage since the stages ofthe method preceding the heating are easier to carry out with arelatively short shrinkage tube than with a long one. Even if theincrease in length achieved by heating is as little as 30 percent it issome help, but it has been found that it is quite easy to obtain anincreased length of over IOO'percent. Considerable increase in. lengthis of particular importance when the whole coil, or a substantial partof it, say percent, is to be provided with a shrinkage .tube. A singlecoherent shrinkage tube for the whole coil is then to be preferred. Byshrinking'one end of the tube which overlaps the other, a tight anduniform casing for the coil can be obtained, particularly if theshrinkage tube at thestart is manufactured with an opening or openingsthrough which to pass through the connection conductors of the coil. Ifsuch is not'the case, holes can be made at suitable points and sealedwith cured resin or the like, or a special lead-in tube, for example ofplastic, can be used, which is provided with a sealing flange arrangedinside the shrinkage tube. In some cases a plurality of tubes or tubeparts can be used for complete covering of the coil, for example tubesor tube parts arranged'one outside the other in expanded condition.

Particularly when the coil is to be insulated for relatively highvoltage, for example 3 10 kV, it-is important to avoid airpocketsbetween the shrinkage tube and the bundle of conductors. In certaincases it may be sufiicient'to provide an insulating layer of resilientsolid material, for example soft rubber, between the bundle ofconductors and the shrinkage tube. Still greater safety against airpockets is achieved if instead an insulating material is used which ismore or less liquid, at least uponheating.

' Especially when using such a liquid material, it is advantageous tocarry out the heating required for shrinkage in a special manner, namelyby successive heating of the parts of the shrinkage tube immediatelyadjacent each other in the longitudinal direction of the tube to fullshrinkage. If the above-mentioned insulating material, for example inthe form of a viscous .paste is supplied at'leastin-the initial stage ofthe heat treatment in a quantity per unit of length of the coilcircumference which is greater than that intended for the finished coil,the progressive heating along the coil will result in a ridge of liquidinsulating material being forced in front of the shrinkage zone so thatthe occurrence of air pockets is prevented. The liquid insulatingmaterial may be applied just before heating is initiated, or at arelatively early stage, for example by coating the bundle of conductorsor the shrinkage tube with a curable resin which solidifies some timeafter being sprayed on and which first melts and then hardens upon beingheated.

Besides the favorable effect mentioned above, heating the coil along asuccessively displaced heating zone has the advantage that the shrinkagetube is stretched more satisfactorily in its longitudinal direction,which is of particular importance when a corrugated shrinkage tube isused. In such cases it may be advisable to subject the shrinkage tube toa reasonable tractive force at the same time that the progressiveheating is taking place. r

BRIEF DESCRIPTION OF THE DRAMNGS In the following the invention will bedescribed with reference to the accompanying drawings in which FIGS. 1,1a and lb illustrate a process according to one form of the invention,and

FIG. 2 a method according to another form. FIGS. 1a and 1b show twoalternatives of a cross-section through A-A in FIG. 1.

FIG. 3 shows a means for heating a shrinkage tube arranged on a coil andFIG. 4 shows in cross-section a coil side provided with a soft rubberlayerbetween the conductor bundle and the shrinkage tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, 1 designates aninsulated conductor having circular or rectangular cross-section. Oneend of the conductor can be attached to the circular frame 2 at a pointP at the bottom of a peripherally running L- shaped groove. The frame 2has a removable part 3. The frame 2 is arranged to be able to rotateunder the influence of a number of driving rollers 4, for example ofrubber. A shrinkage tube 5 is held in position between a pair oftube-holders 6 and 7. 25 is a tensioning means through which theconductor 1 is pulled when being coiled on to the frame 2.

I. With a method according to the invention, carried out with the helpof the device shown in FIG. 1, the circular frame '2 is first opened byremoving the detachable part 3. Then the shrinkage tube is threaded ontothe frame 2 and clamped between the jaws 6 and 7, the

frame part 3 is put in place and the conductor 1 attached by one end atpoint P, after which the frame 2 is rotated and the conductor lis coiledon to the frame 2. When the desired'number of coil turns has been woundon to the frame, the frame part 3 is again removed and also the guide'parts 8'which are arranged parallel to the flange 9 and fixed by meansof radially directed screw bolts during the coiling process. It is noweasy to remove the frame 2 from the coil and the shrinkage tube.

In certain cases, for example when the finished coil is to be shapedwith small radii of curvature, for example as a rectangular coil withrelatively sharp corners, it may be advantageous first to make the coilwith a different shape, for example circular, with the shrinkage tube inposition but not shrunk. If the coil shape is not the same as in theintended final product, this is achieved by drawing and/or pressing inthe radial direction so that the coil is shaped as desired. Thereafterthe shrinkage tube (or tubes) is adjusted to the desired position andsubjected to the heat-treatment required for shrinkage.

In FIG. 2, 20 designates a coil which is wound from an insulatedconductor 21. The coil is provided at two' different points along thecircumference of the coil with a surrounding insulating layer by twoshrinkage tubes 22 and 23 being threaded on to the same end of theconductor and then passed continuously along the entire length of theconductor. Each time a distance equal to the turn length is passed by ashrinkage tube, the conductor end is again threaded into the tube.

FIG. 3 shows a coil insulated according to the invention at a stage inthe manufacture when the final heattreatment has been started but notcompleted. Part of the shrinkage tube 35b fits tightly around theconductor bundle formed of a plurality of coil turns 32, while the restof the shrinkage tube, 35a, has not yet been subjected to the necessaryheat-treatment. The shrinkage tube is corrugated and intended to coverthe coil completely when the heating treatment has been completed. Theheating is carried out with the help of a hollow ring 33 with an inletopening 34 and radially inwardly directed outlet openings 36 for hotair. Thering 33 is passed along the circumference of the coil at asubstantially constant speed. A viscous insulating material hasbeen'inserted in the space between the shrinkage tube and the coilbefore the heat-treatment was started, and in such a quantity that aridge 37 of excess material is pressed before the heating zone all thetime.

In certain cases the time required for the heat-treatment can be reducedby using instead of the heating means shown in FIG. 3 a narrow hot airzone covering the total width of the coil and feeding the coil into thezone by one end so that the central part of the shrinkage tube is heatedfirst and two shrinkage zones then move towards opposite ends of theshrinkage tube and towards the same end of the coil.

In FIG. 4, 55 designates a heated and shrunk shrinkage tube which,together with a layer 54 of relatively soft rubber lying inside,encloses a bundle of conductors 51, each belonging to a correspondingturn of a coil manufactured in the manner described in connection withFIG. 1.

A method according to the invention can be used for manufacturing coilsfor many different purposes in the field of high current, for exampletransformer coils and stator and rotor windings for synchronous and asychronous machines.

As mentioned, shrinkage tubes of known and commercially available typeare shrunk by means of heating. In theorya shrinkage tube operatingaccording to other physical principles is possible, for example in theform of a thin-walled, stiff tube in combination'with an extremelyelastically deformed rubber tube, the shrinkage being effected bydestruction of the stiff tube. If, for example, this is a tube oftoughened glass, the destruction may be carried out mechanically and ifit consists of hard plastic, this may be softened with the help of asuitable solvent. The use of such types of shrinkage tubes is consideredto lie within the scope of the invention.

In both the methods described there is effected such relative movementbetween the first end of the conductor and the sleeve along a length ofconductor corresponding to the perimeter of the coil and thereafter thetube is again fitted over the end of the conductor and the relativemovement is repeated until portions of all the turns of the conductorare enclosed in the sleeve.

I claim:

1. Method of m nufacturing a coil (20) comprising several turns of aninsulated conductor (1 21) and provided with at least one layer ofinsulating material surrounding all the turns, in which such layerconsists essentially of a shrinkage tube (5) of insulating material,

which comprises fitting the tube in expanded state over one end of theconductor and effecting a continuous relative movement between conductorand tube along a length of conductor corresponding to the length of acoil turn, and after each time a coil turn length has been passedfitting the tube over said end of the conductor and efiecting suchrelative movement successively until the tube encloses a portion of allof the coil turns, and shrinking the tube to exert pressure on thebundle of conductors inside.

2. Method according to claim 1, which comprises fitting the shrinkagetube (5) over a frame (2) located in a plane and having an openingintended therefor, and attaching said conductor end to the frame, givingthe frame a rotary movement in said plane in such a way that theconductor is wound with several turns on the frame while at leastpartially limiting the movement of the shrinkage tube in said plane,removing the shrinkage tube from the frame by displacing it along theenclosed bundle of conductors and through said opening, and removing thecoil with the surrounding shrinkage tube from the frame.

3. Method according to claim 1, which comprises coiling said conductor(21) to form the desired number of turns, and thereafter producing suchrelative movement between shrinkage tube (22) and conductor.

4. Method according to claim 1, in which said shrinkage tube in expandedstate is corrugated, whereby when the corrugation is flattened outduring shrinkage an increase in length is produced.

5. Method according to claim 1 in which the final shrinking of theshrinkage tube comprises a progressive shrinking in the longitudinaldirection of the shrinkage tube.

6. Method according to claim 1, which comprises positioning a layer ofyielding insulating material between the coil and the shrinkage tubebefore shrinking the tube.

7. Method according to claim 1, which comprises introducing aninsulating material which is liquid at a temperature lower than or equalto the maximum temperature of the shrinkage tube during shrinking intothe shrinkage tube before shrinking.

8. Method according to claim 7, in which said liquid insulating materialis supplied, at least at the first part of the shrinkage tube to beshrunk, in a quantity per unit length of the coil side greater than theaverage unit quantity intended for the completely insulated coil, andproducing progressive contraction of the tube to effect finaldistribution of this insulating material along the circumference of thecoil.

9. Method according to claim 1, in which the shrinkage tube in shrunkstate surrounds at least of the coil circumference.

10. Method according to claim 1, which comprises applying a plurality ofshrinkage tubes arranged along the coil circumference without contactwith each other.

11. Method according to claim 1, which comprises applying a plurality ofshrinkage tube portions initially and in expanded condition arranged oneoutside the other with a relatively high degree of overlapping, andsubstantially reducing the overlapping prior to the final shrinking.

- e I UNITED STATE PATENT OFFICE CERTIF-ICATEOF CORRECTION Patent N043,-702,499 v Date'd 7 November 14, 197.2

v I nvntor(s)"" 'Lars-Goran'Virsberg 7 It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as "shown below:

, The ihventor's last name is changed from "Virsbreg" to Virsberg Signedand sea-ledthisf8th day of-liay 11 73.

him-M I) I LFLI- TCiE-EJR, J'E. Y ROBLLRT sowscmmc Attesting Officer H 1Commissioner of Patents FORM PO-1050 (10-69) USCOMM-DC scam-Peg UNITEDSTATES PATENT OFFICE 7' CERTIFICATE OF CORRECTION v Patent No.3, 702,499 D t d November 14, 1972 Inventor(s) Lars-Goran Virsberg It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

The inventor's last name is changed from "Virsbreg" to Virsberg Signedand sealed this 8th day of May 1773.

(SEAL) ,Attest:

EDI-MRI) M F LET-31333 J'R 7 R0 5231 GO E SCH-31K Attesting OffioerCommissioner of Patents USCOMM-DC 60376-5 59 9 U.S GOVERNMENT PRINTINGOFFICE: I959 O36G'334 FORM PO-1050 (10-69)

1. Method of manufacturing a coil (20) comprising several turns of aninsulated conductor (1, 21) and provided with at least one layer ofinsulating material surrounding all the turns, in which such layerconsists essentially of a shrinkage tube (5) of insulating material,which comprises fitting the tube in expanded state over one end of theconductor and effecting a continuous relative movement between conductorand tube along a length of conductor corresponding to the length of acoil turn, and after each time a coil turn length has been passedfitting the tube over said end of the conductor and effecting suchrelative movement successively until the tube encloses a portion of allof the coil turns, and shrinking the tube to exert pressure on thebundle of conductors inside.
 2. Method according to claim 1, whichcomprises fitting the shrinkage tube (5) over a frame (2) located in aplane and having an opening intended therefor, and attaching saidconductor end to the frame, giving the frame a rotary movement in saidplane in such a way that the conductor is wound with several turns onthe frame while at least partially limiting the movement of theshrinkage tube in said plane, removing the shrinkage tube from the frameby displacing it along the enclosed bundle of conductors and throughsaid opening, and removing the coil with the surrounding shrinkage tubefrom the frame.
 3. Method according to claim 1, which comprises coilingsaid conductor (21) to form the desired number of turns, and thereafterproducing such relative movement between shrinkage tube (22) andconductor.
 4. Method according to claim 1, in which said shrinkage tubein expanded state is corrugated, whereby when the corrugation isflattened out during shrinkage an increase in length is produced. 5.Method according to claim 1 in which the final shrinking of theshrinkage tube comprises a progressive shrinking in the longitudinaldirection of the shrinkage tube.
 6. Method according to claim 1, whichcomprises positioning a layer of yielding insulating material betweenthe coil and the shRinkage tube before shrinking the tube.
 7. Methodaccording to claim 1, which comprises introducing an insulating materialwhich is liquid at a temperature lower than or equal to the maximumtemperature of the shrinkage tube during shrinking into the shrinkagetube before shrinking.
 8. Method according to claim 7, in which saidliquid insulating material is supplied, at least at the first part ofthe shrinkage tube to be shrunk, in a quantity per unit length of thecoil side greater than the average unit quantity intended for thecompletely insulated coil, and producing progressive contraction of thetube to effect final distribution of this insulating material along thecircumference of the coil.
 9. Method according to claim 1, in which theshrinkage tube in shrunk state surrounds at least 90% of the coilcircumference.
 10. Method according to claim 1, which comprises applyinga plurality of shrinkage tubes arranged along the coil circumferencewithout contact with each other.
 11. Method according to claim 1, whichcomprises applying a plurality of shrinkage tube portions initially andin expanded condition arranged one outside the other with a relativelyhigh degree of overlapping, and substantially reducing the overlappingprior to the final shrinking.